Generally, when a packet data transmission method for group communication on Internet is divided in view of a transmitter and a receiver attending transmission, the packet data transmission method is divided into a unicasting transmission method, a broadcasting transmission method, and a multicasting transmission method.
To be specific, the unicasting transmission method is a one-to-one transmission method that one transmitter, i.e., a server or a terminal, transmits a data packet to another receiver, i.e., a server or a terminal, and has a benefit that the data packet is stably transmitted. However, when the server transmits the same data to a plurality of receivers, the data should be respectively transmitted to the receivers to receive the data. Accordingly, it causes excessive load to the server and transmission efficiency of a network is lowered. At this time, the more the number of receivers increases, the more the problems increase.
The broadcasting transmission method is a method that one transmitter transmits data to the entire receivers on sub-network and has a benefit that the same data are transmitted to the receivers at a time. However, there is also a shortcoming that the receiver not to receive the data should receive the data.
Since the multicasting transmission method is a point-to-multipoint or multipoint-to-multipoint data packet transmission method for simultaneously transmitting a data packet to the terminals requiring data on the same network segment, the multicasting transmission method is proper to group communication as a superior data transmission method.
To have a look at a difference between packets transmitted by the multicasting transmission method and the unicasting transmission method, according to the unicasting transmission method, an Internet application program on Transmission Control Protocol/Internet Protocol (TCP/IP) that the data transmitter marks an Internet Protocol (IP) address of the receiver on a header of the transmission packet and transmits the packet. However, according to the multicasting transmission method, an address of a group that the receivers attend is marked on the header instead of an address of the receiver and the data packet is transmitted. At this time, the group address for multicasting transmission is a D-Class IP address (224.0.0.0˜239.255.255.255) and does not represent an actual host differently from A, B, C-Class IP addresses which represent each worldwide Internet host. Accordingly, the receiver receiving the multicasting packet having the group address determines whether the receiver is included in the packet group and determines whether the receiver accepts the packet.
Currently, since a router on Internet generally does not support the multicasting transmission method, the router transmits a packet encapsulated according to a technique called Tunneling between multicasting routers in order to transmit a multicasting packet on Internet. That is, when the multicasting packet goes through general routers which do not support the multicasting transmission method by adding an IP address of both ends of the tunnel set up between the multicasting routers in front of the header of the data packet having the multicasting address, the multicasting packet is routed by the general routers according to the unicasting data packet transmission method and is finally transmitted to a destination of the tunnel. However, since the unicasting transmission method only supports one-way transmission, it is not proper to the system for real-time interactive communication.
Although there is a group communication method using the unicasting transmission method as well as a group communication method using the conventional multicasting transmission method on Internet, as described above, the unicasting transmission method has the problems that the service is provided to only a few users at a time and a group communication service of a high-quality is not provided to a plurality of receivers due to network traffic generated by respectively transmitting the data packet to the receivers.
As another conventional technology for solving the problem, there is “A method for communication in groups using conversion between multicasting style and unicasting style,” KR Patent No. 10-0586025 issued to Haedenbridge Co., Ltd. on May 26, 2006, which is suggested by the same invention, Namgung, Hwan-Sik as that of this application.
The above patent relates to a method for real-time communication among a plurality of terminals in groups based on interactive multicasting/unicasting conversion on Internet where multicasting packet communication is not supported without increasing of network traffic, and a computer-readable recording media recording a program for realizing the method. To be specific, the group communication method in a group communication system, includes a first step of collecting network information of a terminal accessing for group communication; a second step of checking whether there is another pre-accessing terminal having network information same as the collected network information; a third step of allowing a right for mutually transforming the multicasting packet data into unicasting packet data, and the unicasting packet data into multicasting packet data to a terminal when there is another pre-accessing terminal at the check result, and not allowing the right to the terminal when there is no pre-accessing terminal; and transmitting the unicasting packet data transmitted from the authorized terminal on network to an authorized terminal on another network.
In addition, the group communication method in the terminal includes a first step of logging in the group communication system by a terminal; a second step of allowing a right for mutually transforming multicasting packet data into unicasting packet data, and unicasting packet data into multicasting packet data by a terminal when there is no terminal having network information which is the same as that of the terminal logging in the group communication system; and a third step of transforming multicasting packet data generated in the network including the terminal into unicasting packet data in real-time and transmitting the unicasting packet data to the group communication system, or transforming the unicasting packet data transmitted from the group communication system into multicasting packet data in real-time and transmitting the multicasting packet data to another terminals on own network.
In order to provide interactive group communication or interactive broadcasting to massive distribution terminals in the same session on IP network, a communication method among a plurality of distributed media servers for synchronizing the same sessions and an connection management operating method for connecting a predetermined media server to the massive distribution terminals to receive an optimal service are required. When the distribution terminals are on the same network, a special data transmission method for maintaining network traffic at minimum is required.
A conventional distribution technology of media servers concentrates on a Contents Delivery Network (CDN) field for distributing media contents in the distributed media server in order to distribute overload of Central Processing Unit (CPU) for controlling network load distribution and connection terminal process of the media server mainly in one-way media streaming.